fix(semantic): symbols inside functions and classes incorrectly flagged as exported (#2896)

# What This PR Does

Symbols declared inside exported functions and classes were being
incorrectly flagged with `SymbolFlags::Export`.

For example,
```ts
export function foo<T>(a: T) {
  let b = String(a)
  return b
}
```
`T`, `a`, and `b` were all flagged as exported.

## Further Work
It doesn't seem like exported enums and interfaces are being included in
`ModuleRecord`. Am I looking in the wrong place, or are they actually
missing?

crates/oxc_semantic/src/builder.rs

@@ -1681,6 +1681,7 @@ impl<'a> SemanticBuilder<'a> {
             AstKind::Class(class) => {
                 self.current_node_flags |= NodeFlags::Class;
                 class.bind(self);
+                self.remove_export_flag();
                 self.make_all_namespaces_valuelike();
             }
             AstKind::ClassBody(body) => {
@@ -1700,6 +1701,9 @@ impl<'a> SemanticBuilder<'a> {
             AstKind::BindingRestElement(element) => {
                 element.bind(self);
             }
+            AstKind::FormalParameters(_) => {
+                self.remove_export_flag();
+            }
             AstKind::FormalParameter(param) => {
                 param.bind(self);
             }
@@ -1832,6 +1836,10 @@ impl<'a> SemanticBuilder<'a> {
         }
     }
 
+    fn remove_export_flag(&mut self) {
+        self.current_symbol_flags -= SymbolFlags::Export;
+    }
+
     fn add_current_node_id_to_current_scope(&mut self) {
         self.scope.add_node_id(self.current_scope_id, self.current_node_id);
     }

crates/oxc_semantic/tests/modules.rs

@@ -1,5 +1,7 @@
 mod util;
 
+use oxc_semantic::SymbolFlags;
+use oxc_syntax::module_record::ExportExportName;
 pub use util::SemanticTester;
 
 #[test]
@@ -29,3 +31,140 @@ fn test_exports() {
     // FIXME: failing
     // test.has_some_symbol("defaultExport").is_exported().test();
 }
+
+#[test]
+fn test_exported_named_function() {
+    let test = SemanticTester::js(
+        "
+    export function foo(a) {
+        let x = 1;
+    }
+    ",
+    );
+    test.has_some_symbol("foo").is_exported().test();
+    for name in &["a", "x"] {
+        test.has_some_symbol(name).is_not_exported().test();
+    }
+
+    SemanticTester::ts("export function foo<T>(a: T) { a.length }")
+        .has_some_symbol("T")
+        .is_not_exported()
+        .test();
+}
+
+#[test]
+fn test_exported_default_function() {
+    let test = SemanticTester::js(
+        "
+    export default function foo(a) {
+        let x = 1;
+    }
+    ",
+    );
+    for name in &["a", "x"] {
+        test.has_some_symbol(name).is_not_exported().test();
+    }
+
+    let test = SemanticTester::ts("export default function <T extends string>(a: T) { a.length }");
+    test.has_some_symbol("a").is_not_exported().test();
+    test.has_some_symbol("T").is_not_exported().test();
+}
+
+#[test]
+fn test_exported_named_class() {
+    let test = SemanticTester::ts(
+        "
+    export class Foo<T> {
+        constructor(a) {
+            this.a = a;
+        }
+
+        bar() {
+            return this.a;
+        }
+    }
+    ",
+    );
+
+    test.has_class("Foo");
+    test.has_some_symbol("Foo").is_exported().test();
+    // NOTE: bar() is not a symbol. Should it be?
+    for name in &["a", "T"] {
+        test.has_some_symbol(name).is_not_exported().test();
+    }
+
+    SemanticTester::ts(
+        "
+    class Foo {};
+    export { Foo }
+    ",
+    )
+    .has_some_symbol("Foo")
+    .is_exported()
+    .test();
+}
+
+#[test]
+fn test_exported_default_class() {
+    let test = SemanticTester::ts(
+        "
+    export default class Foo<T> {
+        constructor(a) {
+            this.a = a;
+        }
+    }
+    ",
+    );
+
+    test.has_class("Foo");
+    test.has_some_symbol("a").is_not_exported().test();
+    test.has_some_symbol("T").is_not_exported().test();
+
+    {
+        let foo_test = test.has_some_symbol("Foo");
+        let (semantic, _) = foo_test.inner();
+        let m = semantic.module_record();
+        let local_default_entry = m
+            .local_export_entries
+            .iter()
+            .find(|export| matches!(export.export_name, ExportExportName::Default(_)))
+            .unwrap();
+        assert!(local_default_entry.local_name.name().is_some_and(|name| name == &"Foo"));
+        assert!(!m.exported_bindings.contains_key("Foo"));
+        assert!(m.export_default.is_some());
+        foo_test.contains_flags(SymbolFlags::Export).test();
+    }
+}
+
+// FIXME
+#[test]
+#[ignore]
+fn test_exported_enum() {
+    let test = SemanticTester::ts(
+        "
+        export enum Foo {
+            A = 1,
+            B,
+        }
+    ",
+    );
+    test.has_some_symbol("Foo").is_exported().contains_flags(SymbolFlags::RegularEnum).test();
+    test.has_some_symbol("A").is_not_exported().contains_flags(SymbolFlags::EnumMember).test();
+    test.has_some_symbol("B").is_not_exported().contains_flags(SymbolFlags::EnumMember).test();
+}
+
+// FIXME
+#[test]
+#[ignore]
+fn test_exported_interface() {
+    let test = SemanticTester::ts(
+        "
+        export interface Foo<T> {
+            a: T;
+        }
+        ",
+    );
+    test.has_root_symbol("Foo").is_exported().contains_flags(SymbolFlags::Interface).test();
+    test.has_some_symbol("a").is_not_exported().test();
+    test.has_some_symbol("T").is_not_exported().test();
+}

crates/oxc_semantic/tests/util/symbol_tester.rs

@@ -59,6 +59,11 @@ impl<'a> SymbolTester<'a> {
         }
     }
 
+    /// Get inner resources without consuming `self`
+    pub fn inner(&self) -> (Rc<Semantic<'a>>, SymbolId) {
+        (Rc::clone(&self.semantic), *self.test_result.as_ref().unwrap())
+    }
+
     /// Checks if the resolved symbol contains all flags in `flags`, using [`SymbolFlags::contains()`]
     pub fn contains_flags(mut self, flags: SymbolFlags) -> Self {
         self.test_result = match self.test_result {
@@ -142,12 +147,46 @@ impl<'a> SymbolTester<'a> {
         self.test_result = match self.test_result {
             Ok(symbol_id) => {
                 let binding = self.target_symbol_name.clone();
-                if self.semantic.module_record().exported_bindings.contains_key(binding.as_str())
-                    && self.semantic.scopes().get_root_binding(&binding) == Some(symbol_id)
+                let is_in_module_record =
+                    self.semantic.module_record().exported_bindings.contains_key(binding.as_str())
+                        && self.semantic.scopes().get_root_binding(&binding) == Some(symbol_id);
+                let has_export_flag = self.semantic.symbols().get_flag(symbol_id).is_export();
+                match (is_in_module_record, has_export_flag) {
+                    (false, false) => Err(miette!(
+                            "Expected {binding} to be exported. Symbol is not in module record and does not have SymbolFlags::Export"
+                        )),
+                    (false, true) => Err(miette!(
+                            "Expected {binding} to be exported. Symbol is not in module record, but has SymbolFlags::Export"
+                        )),
+                    (true, false) => Err(miette!(
+                            "Expected {binding} to be exported. Symbol is in module record, but does not have SymbolFlags::Export"
+                        )),
+                    (true, true) => Ok(symbol_id)
+                }
+            }
+            e => e,
+        };
+        self
+    }
+
+    #[allow(clippy::wrong_self_convention)]
+    pub fn is_not_exported(mut self) -> Self {
+        self.test_result = match self.test_result {
+            Ok(symbol_id) => {
+                let binding = self.target_symbol_name.clone();
+                if self.semantic.symbols().get_flag(symbol_id).contains(SymbolFlags::Export) {
+                    Err(miette!("Expected {binding} to not be exported. Symbol has export flag."))
+                } else if self
+                    .semantic
+                    .module_record()
+                    .exported_bindings
+                    .contains_key(binding.as_str())
                 {
-                    Ok(symbol_id)
+                    Err(miette!(
+                        "Expected {binding} to not be exported. Binding is in the module record"
+                    ))
                 } else {
-                    Err(miette!("Expected {binding} to be exported."))
+                    Ok(symbol_id)
                 }
             }
             e => e,

crates/oxc_syntax/src/module_record.rs

@@ -128,11 +128,11 @@ impl NameSpan {
         Self { name, span }
     }
 
-    pub fn name(&self) -> &CompactStr {
+    pub const fn name(&self) -> &CompactStr {
         &self.name
     }
 
-    pub fn span(&self) -> Span {
+    pub const fn span(&self) -> Span {
         self.span
     }
 }
@@ -261,6 +261,13 @@ impl ExportLocalName {
     pub fn is_null(&self) -> bool {
         matches!(self, Self::Null)
     }
+
+    pub const fn name(&self) -> Option<&CompactStr> {
+        match self {
+            Self::Name(name) => Some(name.name()),
+            Self::Default(_) | Self::Null => None,
+        }
+    }
 }
 
 pub struct FunctionMeta {